Retorting bituminous solids



Jan. 10, 1967 R BlDDlCK ETAL 3,297,562

RETORTING BITUMINOUS SOLIDS Filed March 6, 1964 2 Sheets-Sheet l Royce E. Biddick Charles E. Juhnig lnvenrors Charles W. Tyson U" 1/ Patent Attorney Jan. 10, 1967 R. E. BIDDICK ETAL 3,297,562

RETORTING BITUMINOUS SOLIDS 2 Sheets-Sheet 2 Filed March 6, 1964 FIG-2 FIG-5 FIG-3 FIG-4 Royce EL Biddick Inventors Charles E. Juhnig Charles W. Tyson By 7/ f 7 PclfentArrorney United States Patent 3,297,562 RETORTING BITUMINOUS SOLIDS Royce E. Biddick, Minneapolis, Minn., and Charles E.

Jal nig, Rumson, and Charles W. Tyson, Summit, N.J.,

assignors to Esso Research and Engineering Company,

a corporation of Delaware Filed Mar. 6, 1964, Ser. No. 350,020 Ciairns. (Cl. 208-11) This invention relates to a method for recovering valuable hydrocarbons from shale and the like.

As is known, ordinary oil shale does not contain oil as such but a solid bitumen material or oil-forming mateterial known as kerogen which when heated and retorted or distilled breaks down into gases, hydrocarbon liquids and carbon or coke.

Oil shale is crushed or broken down into small lumps or particles and then heated to a temperature of about 800 F.l200 F. The released hydrocarbons are withdrawn either as vap-orous material or as condensed liquid products.

In one form of the invention, oil shale particles are continuously passed downwardly through a succession of zones as a relatively compact, moving bed wherein they are heated by countercurrent flow of gases leaving the combustion or hot zone. Going from top to bottom the oil shale particles pass thrugh a preheating zone, a retorting zone and a burning or combustion zone. Preferably the zones are in one vessel but may be formed of separate connected vessels. The moving solids bed or column has a void space of about 35% to 50%.

The preheating zone serves to preheat the incoming shale particles and may be used to cool the retorted vapors. The retorted vapors are further cooled to recover liquid shale oil and to separate combustible gas which can be recovered as such or at least in part burned in the combustion zone to supply additional heat for the retorting zone. The preheated shale particles then pass to the retorting zone where they are heated by hot combustion or flue gases coming from the combustion zone. Part or all of the retorted vapors are passed up through the preheating zone.

The spent shale particles from the retorting zone are passed to the combustion zone where the carbonaceous material or coke on the spent shale is burned with an oxygencontaining gas such as air. Also, extraneous fuel such as some of the recovered gas as above mentioned may be burned here to add heat to the flue gas to be passed to the retorting zone. Some of the flue gas or combustion gases from the combustion zone may be passed directly to the preheating zone, if desired, to supply heat to the shale particles being preheated.

In the knowncontinuous shale retorts, the operation is inflexible and the time of heating in the retorting zone cannot be varied readily, since it is set by the temperature profile in the bed. If the residence time of the shale particles in the retorting zone at a high temperature is too short, the method is ineflicient in that the inner portions of the larger oil shale lumps will not be fully retorted before entering the combustion zone. The present invention provides a method for increasing the time of residence of the shale lumps in the retorting zone to improve the recovery of oil.

Channels or tubes are provided for by-passing the combustion gases around at least a portion of the solid shale particles in the retorting zone. The tubes or channels may be mounted internally or externally of the retorting zone but in communication therewith. The solid shale particles pass down around the tubes when mounted internally but some of the gas and/ or vapor bypasses the shale solids and passes up through the tubes in the shale solids moving bed to a higher region. In this way the Patented Jan. 10, 19%? "ice heated oil shale particles from the preheat zone are allowed to spend a longer time at desired retorting temperatures of approximately 800 F.l200 F. before entering the combustion zone. In other words, a soaking zone is provided between the preheat and combustion zones to assure complete retorting and maximize oil recovery. Without it, independent control of retorting time and temperature is not possible, since the temperature profile in the bed is set by the relative flow rates of .gas and solids.

Increased residence time at the selected desired temperature permits heat diffusion to the inner portions of the large lumps of shale which would otherwise pass into the combustion or hot zone before being fully retorted. This unretorted oil would be lost by combustion or be severely cracked to gas and coke. The channels or tubes in eiiect increase the length of the retorting zone and in this way increase the time of retorting.

In the drawings:

FIG. 1 represents a vertical longitudinal cross section of one form of apparatus adapted to practice the process of the present invention;

FIG. 2 represents an enlarged vertical longitudinal cross section of one form of retorting zone or section provided with internal vertical tubes as shown in FIG. 1;

FIG. 3 represents an enlarged vertical longitudinal cross section of another form of retorting zone provided with external tubes communicating with the retoiting zone interior;

FIG. 4 represents an enlarged vertical longitudinal cross section of another form of retorting zone provided with external tubes communicating with the retorting zone interior and having screens or venetian blinds at their inlets and outlets; and

FIG. 5 represents a detail taken on line 55 of FIG. 3 to show the positioning of the deflectors for the tubes.

Referring now to the drawing, the reference character 10 designates a cylindrical shale treating apparatus made up of superimposed vessels or zones in vertical alignment and which may if desired be enclosed in a single exterior vessel. The top zone or vessel 12 is a shale preheating zone which has a dome-shaped top 14 through which extends a funnel-shaped inlet 16 having its lower cylindrical end 18 extending into the zone 12 a short distance and having its funnel end above the zone 12 for receiving shale particles to be treated. The bottom of preheating zone 12 is formed as an inverted truncated cone 22 with a cylindrical or tubular lower end 24 which extends through the dome-shaped top 26 of retorting zone or section 28 for conducting shale particles from preheating zone 12 to retorting zone 28.

The shale particles are not fluidized in any of the zones of the apparatus 10. The lower end 18 of funnelshaped inlet 16 determines the level 32 of the shale solids in preheating zone 12 to leave an annular space 34 surrounding lower end 18 for collecting vapors and gases passing up through the downwardly moving shale particles in pre- :heating zone 12. These vapors and gases are product gaseous material formed by retorting shale and include hydrocarbon vapors and gases and combustion gases which are removed from annular space 34 through line or pipe 36. These product gases and vapors will also contain water or steam and other gases if such gases are introduced in any of the zones forming the shale treating apparatus and including preheating zone or vessel 12, retorting zone or vessel 28 and combustion and shale cooling zone or vessel 38 arranged below retorting vessel or zone 23 and presently to be described in greater detail.

The oil products from retorting are vaporized and carried out with the combustion gas. An important part of the shale oil product leaves in the form of a mist or fog which is formed when the heavy vapors from retorting are cooled as they pass through the shale preheating bed 12.

The. gaseous products pass through line 36 and condenser 42 to condense normally liquid hydrocarbons and the condensed mixture is passed to separator 44 to separate gases from liquid. In some cases it may be desirable or necessary to demist the vapors by passing them through an oil scrubber or an electric precipitator. The liquid which comprises shale oil is withdrawn from separator 44 through line 46 and further treated as necessary or desired. The gaseous material which contains gaseous hydrocarbons is withdrawn overhead from separator 44 through line 48 and utilized as a fuel, if desired, or discarded. At least a portion of the gaseous material may be passed through line 52 and into combustion vesssel or zone 38 to be burned and to supply additional heat of retorting. As shown, the gaseous material is introduced at the bottom of vesssel or zone 38 below stoker bars 54, but, if desired, the gaseous material from line 52 may be introduced into zone 38 above bars 54.

The downward movement of the shale particles in vessels or zones 12, 28 and 38 is controlled by shaker bars or other simiar devices 54 arranged in the bottom of each vesssel or zone 12, 28 and 38, substantially at the top of the inverted truncated conical outlet of each vessel or zone 12, 28 and 38. The holdup of the shale moving bed in apparatus and in zones or vesssels 12, 28 and 38 is controlled by valve 56 mounted in bottom of cylindrical or tubular outlet line 58 extending downwardly from combustion and shale cooling zone 38. The Valve 56 also indirectly controls the rate of introduction of oil shale solids into the top preheating vessel 12 through inlet 16, since the upper level 32 is determined by the angle of repose of the solids.

Preheating vessel 12 has lower tube or cylindrical discharge end 24 which extends into retorting vessel or zone 28 a short distance to determine the level 62 of shale in retorting vessel 28 and to form an annular space 64 around lower tube 24 for receiving retorted gaseous shale products, which may also contain combustion gases. The gaseous products are withdrawn from space 64 and passed through line or pipe 66 into the lower portion of preheating zone 12. Part or all of this gas stream may be withdrawn through line 67 and fed directly to the product recovery system such as separator 44. As shown, the pipe 66 leads from dome-shaped top 26 to the inverted truncated conical portion 22 of preheating vessel 12. If desired, the outlet from pipe 66 may extend higher or enter preheating vessel 12 above bars 54, in which case multiple pipes 66 are desirable. Although most of the oil products are in the form of vapor or mist and so pass through preheating zone or vessel 12, some of the heavy ends may condense on the solids and be recycled to the retoring vessel to be further cracked or coked.

The retorting vessel 28 is provided with a plurality of vertically arranged internal channels or tubes 72 shown in enlarged detail in FIG. 2. There are only two tubes shown but only one or any desired number may be used. The tubes 72 are shown as being of the same length but in some cases the tubes 72 may be of different lengths with some being half the length, etc., to give further control over the time-temperature history of the shale particles. For example, part of the gas may be bypassed through longer tubes, while a smaller portion flows through the shorter tubes to aid in stripping out the oil.

The tubes 72 are rigidly mounted in any suitable manner entirely within the retorting vessel 28 to be held in a vertical position parallel to the wall of the retorting vessel 28. The tubes 72 are open-ended and to prevent downwardly moving shale particles entering the tops of the tubes 72 there are provided deflectors 74 which are inverted V-shaped in vertical cross section and of a slightly larger diameter than the outside diameter of the tube 72. The deflectors 74 are spaced from the upper ends of the tubes to leave a space 76 for gases to pass.

Similarly shaped inverted V-shaped deflectors 78 are vent entry of shale solids into the tubes.

78 are spaced from the ends of the tubes to permit up-' provided for the bottom ends of the tubes 72 to pre- The deflectors flowing gaseous material to bypass the downwardly moving shale bed for a selected region or portion in the retorting vessel 28. The tubes extend for about A to of the length or height of the retorting vessel 28. With the deflectors in position it is intended to pass only hot gases without solids through the tube or tubes 72.

In the preferred form, hot gases, at least in part, are passed from the bottom of the retorting vessel 28 to the top portion of the vessel 28 to bypass only a portion of the downwardly moving compact bed in retorting vessel 28.

The bottom portion 82 of retorting vessel 28 is of inverted truncated conical shape and is provided at its lower end with tube or cylinder 84 which extends down through dome-shaped top 86 of shale cooling and burner vessel or zone 38 a short distance to determine the level 88 of the shale particles in burner vessel or zone 38 and to form annular space 92 around tube 84 in the upper part of vessel 38.

Line or pipe 94 connects space 92 in vessel 38 with retorting vessel or zone 28 and is provided to conduct hot combustion gases from zone or vessel 38 to the bottom portion of retorting vessel or zone 28. Air or other oxygen-containing gas is introduced into the lower portion of burner vessel and shale cooling vessel or zone 38 through one or more lines 95 to burn carbonaceous material from the spent shale particles introduced into burner vessel 38 from retorting vessel 28.

Another line or pipe 96 provided with valve 98 communicates with the top space 92 in burner vessel 38 and leads to the bottom portion of preheating vessel or zone 12 for introducing all or a part only of the hot combustion gases from burner vessel 38 into the preheating vessel 12 if necessary or desired. In this way it is possible to pass substantially all of the hot combustion gases from burner vessel 38 directly to vessel 12 and to bypass vessel 28 which then becomes a soaking vessel. Then it is feasible to draw product vapors off vessel 28 more or less free from flue gases so that recovery of oil is easier.

In FIG. 3 there is shown a modification of the channels or tubes. Here, again, only two of the channels or tubes 102 are shown but more may be used, if desired. In this form the tubes 102 are U-shaped and are vertically arranged to extend externally of the retorting vessel 28. The tubes 102 are arranged to have each arm of the U-shaped tube extend through the wall into the vessel 28 a short distance and to have the rest of the U-shaped tube external of the vessel 28. The upper open end of the top arm 104 opens into the interior of vessel 28 and is provided with a deflector 106 which is inverted V- shaped in vertical cross section and of a slightly larger diameter than the opening in arm 104. It is arranged to have its point 107 at the top near the top of tube 104.

Deflector 106 is rigidly mounted in any'suitable manner in spaced relation to the outlet end of top arm 104 to permit gaseous material to pass from tube or channel 102 and arm 104 into vessel 28. A similar deflector 108 is provided for the lower open end of bottom arm 112 to permit a part of the gaseous material to enter bottom arm 112 from retorting zone 28 and pass through channel or tube 102 to bypass the shale solids between inlet 112 and outlet 104 of channel or tube 102. A damper valve 113 is provided for each channel or tube 102 to control the amount of hot combustion gas bypassing the bed of shale particles undergoing retorting.

FIG. 4 is a similar arrangement to that shown in FIG. 3 with the difference that the ends 114 of U-shaped channel or tube 116 do not extend through the wall of the retorting zone or vessel 28 and are substantially flush with the interior of the wall of the vessel 28. Perforations, screens or venetian blinds 115 are diagrammatically shown as mounted on the inlet inner portions of arms 114 of the channel or tube 116 to prevent entry of shale solids into tube 116. The tube 116 is provided with a damper valve 118 in each channel or tube 116 to control the amount of hot gases passing through the tube or channel 116.

In another form similar to that shown in FIG. 3 the ends of the tubes like 104 and 112 extend into the zone 28 but have box-like enclosures on their inner ends and these enclosures have openings in their bottom wall only to permit gases to bypass at least a portion of the shale bed being retorted as in the other forms of the invention.

In operation, cool crushed raw shale of a particle size between about inch and 2 inches is introduced into the apparatus from funnel-shaped inlet 16 and passed down as a relatively compact nonfluidized mass through preheating vessel 12 where the shale particles are preheated to a temperature between about 500 F. and 7750 F., preferably about 650 F. The shale particles are preheated by countercurrently upflowing hot gases of combustion and retorted shale vapors and gases passing up from retorting vessel 28 and combustion vessel 38.

In passing through preheating vessel 12 the hot retorted products are cooled to a temperature between about 200 F. and 500 F. and some of the high boiling hydrocarbons may condense and be deposited on the shale particles for recycle to the retorting zone 28. The vaporous and mist shale retorted products are withdrawn from the space 34 at the top of preheating zone and passed through condenser 42 and mist separation (not shown), and cooled to a temperature of about 100 F. to 150 F. and the shale oil separated in separator 44 and withdrawn through line 46.

The preheated shale particles pass from zone 12 to retorting zone or vessel 28 and are heated to a temperature between about 800 F. and 1200 F. with a preferred temperature of about 1000 F. The shale particles are maintained in retorting vessel 28 for a residence time between about and 2 hours, preferably about hour.

In the retorting zone the tubes 72 provide channels for a part of the hot gases to bypass the bed of shale particles so as to decrease the heat exchange between the hot gases and the oil shale particles in the retorting vessel and this allows the oil shale to spend a longer time in the retorting vessel at a retorting temperature of about 800 F.1000 F. which is optimum for most shales. The hot gases which are not bypassed contact the shale particles outside the tubes 72 and supply the heat necessaryfor optimum retorting. In addition, the hot gases which bypass the shale bed pass from the lower portion of the bed in retorting vessel 28 and up through the channels or tubes 72 and are introduced into the upper portion of the shale bed in the retorting vessel to supply heat thereto so that the shale particles in the shale bed are more quickly brought up to retorting temperature. The amount of hot gases passing up through tubes 72 is about 20 to 95 vol. percent of the total of hot gases passing up through retorting vessel 28.

The spent shale particles leaving the retorting vessel 28 are now largely free of hydrocarbon materials but contain coke or carbonaceous deposits resulting from the decomposition of the kerogen.

The spent shale particles are passed down through tube 84 into the combustion vessel 38. Air introduced through line 95 into the lower portion of the shale bed is heated up and causes burning of the coke deposit to produce hot gases of combustion which are passed up through the shale bed countercurrently and through line 94 into the shale retorting vessel 38. The shale particles are cooled by the air being preheated. Additional heat may be removed from the hot spent shale by injecting or introducing hydrocarbon gas made in the process via line 52. Other gas or fluid, such as flue gas, inert gas, water or steam, or the like, may be introduced through line 52 and below bars 54 to independently control the oxygen being supplied by the air or oxygen-containing gas and also to control the heat capacity of the gases used to supply the heat of retorting the shale in vessels 12, 28, and 38.

The temperature in the combustion vessel 28 is between about 1000" F. and 1600 F., preferably about 1300 F. The spent shale particles are withdrawn via pipe 58 at a temperature of about 200 F. to 700 F. and discarded.

In a commercial design where the retorting vessel is about 17 feet in diameter and has a straight side length (from the bottom of dome-shaped top 26 and the top of inverted truncated conical bottom 82) of about 15 feet,

about 25 tubes 72 will be provided. Each tube has an inside diameter of about 12 inches and a length of about 10 feet. The deflectors 74 are spaced from the ends of the tubes by about 6 inches.

The oil shale to be used such as Colorado shale contains, for example, about 30 gallons of shale oil per ton of shale, by Fischer assay test.

Table I presents pertinent data applicable to the present invention.

1 Average.

Other types of retorting vessels for shale may be used with the present invention. For example, a retort where the shale particles are forced upwardly by a controlled reciprocating piston feeder through the retort countercurrent to downwardly passing heating fluid may be used. In this apparatus the retorting section or zone is provided with tubes or channels like tubes 72 in FIG. 1 but in this case the hot gas passing down bypasses the upflowin'g compact shale bed in the retorting section.

In a 2000 ton/unit about 15,000 set. of air per ton of shale are passed up through the vessel 10. The oil shale is ground and screened to a particle size of 0.25 to 4 inches. The combustion gas temperature in the re torting zone is about 1300 F. About by volume of the total hot gas is passed through tubes 72 to bypass the movng bed of shale in retorting vessel 28. The temperature of the spent shale is about 300 F. Shale oil recovered is about 250 F. About 25 gallons of oil per ton of shale are obtained and this oil has a gravity of about 19 API, an initial boiling point of about 415 F. and 70% over at 870 F. The Conradson Carbon number is about 5.2 and the S.S.U. viscosity at F. is about 235.

The daily production of shale oil is about 1500 b./d. using the tubes 72 in the retorting vessel 28. In a conventional retorting process not using channels or bypass tubes 72, the shale oil production would be less due to the lower yield of oil caused by inefficient retorting ahead of the combustion zone.

If the direction of movement of the shale bed is upwardly, the deflectors shown in the drawing will be reversed to prevent entry of solids into the bypass channels.

What is claimed is:

1. A process for recovering oil from oil bearing shale solids which comprises preheating the shale solids in a preheating zone, passing the thus preheated solids as a downwardly moving compact solids column into and through a retorting zone wherein the solids are retorted by countercurrent contact with upwardly flowing hot gases, providing at least one stationary, substantially vertical, iby-pass channel within the downwardly moving shale bed in said retorting zone, passing at least a portion of the upwardly flowing hot gases and only hot gases without any substantial amount of solids upwardly through said by-pass channel from a lower region to a higher region within said retorting zone to bypass a section of said downwardly moving shale bed in said retorting zone to supply heat to an upper portion of said retorting zone and into the downwardly moving shale solids bed therein, and removing retorted oil vapors and hot gases overhead from said retorting zone.

2. A process according to claim 1 wherein the hot gases and vapors from said retorting zone are used at least in part for preheating the shale solids in said preheating zone.

3. A process according to claim 1 wherein the retorted solids from said retorting zone are .passed to a burning zone where combustible material on said solids is burned to produce hot combustion gases which are used at least in part as the hot gases for direct contacting and retorting solids in said retorting zone.

4. A process according to claim 1 wherein the retorted solids from said retorting zone are passed to a burning zone where combustible material on said solids is burned to produce hot combustion gases which are used at least in part as hot gases passing to said preheating zone.

5. A process according to claim 1 wherein a plurality of by-pass channels are used and certain of said channels are shorter than others whereby shorter by-pass paths are provided within said retorting zone for said upfiowing hot gases. I

6. A process according to claim 1 wherein said by-pass channel extends for about to /6 of the height of said retorting zone.

7. A process for recovering oil from oil shale solids which comprises passing said solids as a compact downwardly moving bed through a preheating zone, a retorting zone and a combustion zone, passing -hot gases including combustion gases upwardly countercurrent to said downwardly moving bed of shale solids in said preheating zone, burning in said burning zone carbonaceous material from the spent shale solids passed from said retorting zone to supply at least part of said hot gases 'for upward passage through said shale soilds moving bed, passing at least a portion of said hot gases from said burning zone into the loyer portion of and through said retorting zone for retorting shale solids moving therethrough, providing stationary vertical substantially solids-free passages in said moving shale solids bed within said retorting zone to bypass at least a portion of the hot gases from the bottom portion of said retorting zone to the upper portion of said retorting zone and around a portion of said downwardly moving shale solids in said retorting zone to provide extended heating of the large shale solids in said shale solids bed and to increase the time of heat soaking of said large oil shale solids in said retorting zone, passing at least a portion of retorted vapors and hot gases from said retorting zone through said preheating zone to preheat solids and cool retorted vapors, removing retorted vapors and gases from said preheating zone and recovering shale oil from said retorted vapors.

8. A process according to claim 7 wherein at least part of the gases separated from said retorted vapors is passed to said combustion zone, and burned along with the carbonaceous material on the spent shale particles.

9. A process for recovering oil from oil shale solids which comprises passing oil shale solids as a downwardly moving compact bed in succession through a preheating zone, a retorting zone and combustion zone, passing an oxygen-containing gas into said combustion zone to burn carbonaceous residue on said oil-bearing shale solids, withdrawing hot =flue gas produced thereby and passing at least a part thereof upwardly through said retorting zone to supply heat of retorting, bypassing at least a part of said upfiowing hot flue gas from a lower region to a higher region within said bed in said retorting zone around a vertical region of said downwardly moving compact bed within said retorting zone to provide extended heating of large shale solids in said shale solids bed during retorting and to increase time of retorting and soaking at the selected temperature and removing retorted shale products from said retorting zone.

10. A process for recovering oil from oil shale solids which comprises passing oil shale solids as a downwardly moving compact bed in succession through a preheating zone, a retorting zone and a combustion zone, passing an oxygen-containing gas into the lower portion of said combustion zone to burn carbonaceous residue on said shale solids, withdrawing hot flue gas produced thereby from the upper portion of said combustion zone and passing at least a part thereof upwardly through said downwardly moving bed of shale solids in said retorting zone to sup ply heat of retorting, bypassing said downwardly moving bed of shale solids with at least a part of said upfiowing hot fine gas from a lower region in said retorting zone to a higher region in said retorting zone without directly contacting a vertical section of said downwardly moving compact bed of shale solids within said retorting zone, said bypassed hot line gas passing through at least one confined passageway external to said retorting zone to increase the temperature of the shale solids in the upper part of said moving bed of shale solids so as to provide extended heating of shale solids in said shale solids bed as they move downwardly through said retorting zone during retorting and to increase the time of retorting and soaking of said shale solids at the selected temperature and removing retorted shale products overhead from said retorting zone.

References Cited by the Examiner UNITED STATES PATENTS 2,448,223 8/ 1948 Lantz 20137 2,560,767 7/1951 Hufi 20137 2,879,208 3/1959 Brice 20137 FOREIGN PATENTS 107,907 7/1939 Australia. 154,695 1/1954 Australia.

DANIEL E. WYMAN, Primaly Examiner. P. KONOPKA, Assistant Examiner. 

1. A PROCESS FOR RECOVERING OIL FROM OIL BEARING SHALE SOLIDS WHICH COMPRISES PREHEATING THE SHALE SOLIDS IN A PREHEATING ZONE, PASSING THE THUS PREHEATED SOLIDS AS A DOWNWARDLY MOVING COMPACT SOLIDS COLUMN INTO AND THROUGH A RETORTING ZONE WHEREIN THE SOLIDS ARE RETORTED BY COUNTERCURRENT CONTACT WITH UPWARDLY FLOWING HOT GASES, PROVIDING AT LEAST ONE STATIONARY, SUBSTANTIALLY VERTICAL, BY-PASS CHANNEL WITHIN THE DOWNWARDLY MOVING SHALE BED IN SAID RETORTING ZONE, PASSING AT LEAST A PORTION OF THE UPWARDLY FLOWING HOT GASES AND ONLY HOT GASES WITHOUT ANY SUBSTANTIAL AMOUNT OF SOLIDS UPWARDLY THROUGH SAID BY-PASS CHANNEL FROM A LOWER REGION TO A HIGHER REGION WITHIN SAID RETORTING ZONE TO BYPASS A SECTION OF SAID DOWNWARDLY MOVING SHALE BED IN SAID RETORTING ZONE TO SUPPLY HEAT TO AN UPPER PORTION OF SAID RETORTING ZONE AND INTO THE DOWNWARDLY MOVING SHALE SOLIDS BED THEREIN, AND REMOVING RETORTED OIL VAPORS AND HOT GASES OVERHEAD FROM SAID RETORTING ZONE. 